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INTRODUCTION: Genome-wide association studies (GWAS) are fundamental for identifying loci associated with diseases. However, they require replication in other ethnicities. METHODS: We performed GWAS on sporadic Alzheimer's disease (AD) including 539 patients and 854 controls from Argentina and Chile. We combined our results with those from the European Alzheimer and Dementia Biobank (EADB) in a meta-analysis and tested their genetic risk score (GRS) performance in this admixed population. RESULTS: We detected apolipoprotein E ε4 as the single genome-wide significant signal (odds ratio = 2.93 [2.37-3.63], P = 2.6 × 10-23 ). The meta-analysis with EADB summary statistics revealed four new loci reaching GWAS significance. Functional annotations of these loci implicated endosome/lysosomal function. Finally, the AD-GRS presented a similar performance in these populations, despite the score diminished when the Native American ancestry rose. DISCUSSION: We report the first GWAS on AD in a population from South America. It shows shared genetics modulating AD risk between the European and these admixed populations. HIGHLIGHTS: This is the first genome-wide association study on Alzheimer's disease (AD) in a population sample from Argentina and Chile. Trans-ethnic meta-analysis reveals four new loci involving lysosomal function in AD. This is the first independent replication for TREM2L, IGH-gene-cluster, and ADAM17 loci. A genetic risk score (GRS) developed in Europeans performed well in this population. The higher the Native American ancestry the lower the GRS values.
Assuntos
Doença de Alzheimer , Azidas , Estudo de Associação Genômica Ampla , Humanos , Chile , Doença de Alzheimer/genética , Predisposição Genética para Doença/genética , Polimorfismo de Nucleotídeo Único/genéticaRESUMO
This work aims to clarify the effect of dietary polyunsaturated fatty acid (PUFA) intake on the adult brain affected by amyloid pathology. McGill-R-Thy1-APP transgenic (Tg) rat and 5xFAD Tg mouse models that represent earlier or later disease stages were employed. The animals were exposed to a control diet (CD) or an HFD based on corn oil, from young (rats) or adult (mice) ages for 24 or 10 weeks, respectively. In rats and mice, the HFD impaired reference memory in wild-type (WT) animals but did not worsen it in Tg, did not cause obesity, and did not increase triglycerides or glucose levels. Conversely, the HFD promoted stronger microglial activation in Tg vs. WT rats but had no effect on cerebral amyloid deposition. IFN-γ, IL-1ß, and IL-6 plasma levels were increased in Tg rats, regardless of diet, while CXCL1 chemokine levels were increased in HFD-fed mice, regardless of genotype. Hippocampal 3-nitrotyrosine levels tended to increase in HFD-fed Tg rats but not in mice. Overall, an HFD with an elevated omega-6-to-omega-3 ratio as compared to the CD (25:1 vs. 8.4:1) did not aggravate the outcome of AD regardless of the stage of amyloid pathology, suggesting that many neurobiological processes relevant to AD are not directly dependent on PUFA intake.
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Doença de Alzheimer , Ácidos Graxos Ômega-3 , Camundongos , Ratos , Animais , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Encéfalo/patologia , Camundongos Transgênicos , Amiloide , Modelos Animais de Doenças , Ratos Transgênicos , Dieta HiperlipídicaRESUMO
The use of fixed fibroblasts from familial and sporadic Alzheimer's disease patients has previously indicated an upregulation of mitochondria-ER contacts (MERCs) as a hallmark of Alzheimer's disease. Despite its potential significance, the relevance of these results is limited because they were not extended to live neurons. Here we performed a dynamic in vivo analysis of MERCs in hippocampal neurons from McGill-R-Thy1-APP transgenic rats, a model of Alzheimer's disease-like amyloid pathology. Live FRET imaging of neurons from transgenic rats revealed perturbed 'lipid-MERCs' (gap width <10â nm), while 'Ca2+-MERCs' (10-20â nm gap width) were unchanged. In situ TEM showed no significant differences in the lipid-MERCs:total MERCs or lipid-MERCs:mitochondria ratios; however, the average length of lipid-MERCs was significantly decreased in neurons from transgenic rats as compared to controls. In accordance with FRET results, untargeted lipidomics showed significant decreases in levels of 12 lipids and bioenergetic analysis revealed respiratory dysfunction of mitochondria from transgenic rats. Thus, our results reveal changes in MERC structures coupled with impaired mitochondrial functions in Alzheimer's disease-related neurons.This article has an associated First Person interview with the first author of the paper.
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Doença de Alzheimer , Retículo Endoplasmático , Mitocôndrias , Neurônios , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Animais , Modelos Animais de Doenças , Retículo Endoplasmático/genética , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/patologia , Humanos , Mitocôndrias/genética , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Neurônios/metabolismo , Neurônios/patologia , Ratos , Ratos TransgênicosRESUMO
Alzheimer's disease (AD) is associated to depressed brain energy supply and impaired cortical and hippocampal synaptic function. It was previously reported in McGill-R-Thy1-APP transgenic (Tg(+/+)) rats that Aß deposition per se is sufficient to cause abnormalities in glucose metabolism and neuronal connectivity. These data support the utility of this animal model as a platform for the search of novel AD biomarkers based on bioenergetic status. Recently, it has been proposed that energy dysfunction can be dynamically tested in platelets (PLTs) of nonhuman primates. PLTs are good candidates to find peripheral biomarkers for AD because they may reflect in periphery the bioenergetics deficits and the inflammatory and oxidative stress processes taking place in AD brain. In the present study, we carried out a PLTs bioenergetics screening in advanced-age (12-14 months old) control (WT) and Tg(+/+) rats. Results indicated that thrombin-activated PLTs of Tg(+/+) rats showed a significantly lower respiratory rate, as compared to that measured in WT animals, when challenged with the same dose of FCCP (an uncoupler of oxidative phosphorylation). In summary, our results provide original evidence that PLTs bioenergetic profiling may reflect brain bioenergetics dysfunction mediated by Aß plaque accumulation. Further studies on human PLTs from control and AD patients are required to validate the usefulness of PLTs bioenergetics as a novel blood-based biomarker for AD.
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Doença de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Plaquetas/metabolismo , Metabolismo Energético/fisiologia , Hipocampo/metabolismo , Placa Amiloide/metabolismo , Animais , Mitocôndrias/metabolismo , Ratos , Ratos TransgênicosRESUMO
Diet is a modifiable risk factor for Alzheimer's disease (AD), but the mechanisms linking alterations in peripheral metabolism and cognition remain unclear. Since it is especially difficult to study long-term effects of high-energy diet in individuals at risk for AD, we addressed this question by using the McGill-R-Thy1-APP transgenic rat model (Tg(+/-)) that mimics presymptomatic AD. Wild-type and Tg(+/-) rats were exposed during 6months to a standard diet or a Western diet (WD), high in saturated fat and sugar. Results from peripheral and hippocampal biochemical analysis and in situ respirometry showed that WD induced a metabolic syndrome and decreased presynaptic bioenergetic parameters without alterations in hippocampal insulin signaling or lipid composition. Cognitive tests, ELISA multiplex, Western blot, immunohistochemistry and RT-qPCR indicated that WD worsened cognition in Tg(+/-) rats, increased hippocampal levels of monomeric Aß isoforms and oligomeric species, promoted deposits of N-Terminal pyroglutamate-Aß (AßN3(pE)) in CA1 pyramidal neurons and interneurons, decreased transcript levels of genes involved in neuroprotective pathways such as Sirtuin-1 and increased nitrated proteins. Our results support the concept that in the presence of early Aß pathology, diet-induced metabolic dysfunctions may contribute as a "second hit" to impair cognition. Noteworthy, such effect is not mediated by higher microglia activation or disruption of blood brain barrier. However, it may be attributed to increased amyloidogenic processing of amyloid precursor protein, generation of AßN3(pE) and dysregulation of pathways governed by Sirtuin-1. This evidence reinforces the implementation of prophylactic interventions in individuals at risk for AD.
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Doença de Alzheimer/complicações , Precursor de Proteína beta-Amiloide/metabolismo , Dieta Ocidental/efeitos adversos , Transtornos da Memória/etiologia , Ácido Pirrolidonocarboxílico/metabolismo , Adiposidade , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/genética , Animais , Cognição , Modelos Animais de Doenças , Metabolismo Energético , Deleção de Genes , Hipocampo/metabolismo , Humanos , Inflamação/complicações , Inflamação/genética , Inflamação/metabolismo , Masculino , Transtornos da Memória/metabolismo , Ratos , Ratos TransgênicosRESUMO
In the Drosophila brain, the neuropeptide PIGMENT DISPERSING FACTOR (PDF) is expressed in the small and large Lateral ventral neurons (LNvs) and regulates circadian locomotor behavior. Interestingly, PDF immunoreactivity at the dorsal terminals changes across the day as synaptic contacts do as a result of a remarkable remodeling of sLNv projections. Despite the relevance of this phenomenon to circuit plasticity and behavior, the underlying mechanisms remain poorly understood. In this work we provide evidence that PDF along with matrix metalloproteinases (Mmp1 and 2) are key in the control of circadian structural remodeling. Adult-specific downregulation of PDF levels per se hampers circadian axonal remodeling, as it does altering Mmp1 or Mmp2 levels within PDF neurons post-developmentally. However, only Mmp1 affects PDF immunoreactivity at the dorsal terminals and exerts a clear effect on overt behavior. In vitro analysis demonstrated that PDF is hydrolyzed by Mmp1, thereby suggesting that Mmp1 could directly terminate its biological activity. These data demonstrate that Mmp1 modulates PDF processing, which leads to daily structural remodeling and circadian behavior.
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Ritmo Circadiano/genética , Proteínas de Drosophila/genética , Metaloproteinase 1 da Matriz/genética , Plasticidade Neuronal/genética , Neuropeptídeos/genética , Animais , Animais Geneticamente Modificados , Comportamento Animal , Drosophila melanogaster , Atividade Motora/genética , Neurônios/metabolismo , Neurônios/fisiologiaRESUMO
Studies of post-mortem brains from Alzheimer disease patients suggest that oxidative damage induced by mitochondrial amyloid ß (mitAß) accumulation is associated with mitochondrial dysfunction. However, the regulation of mitAß metabolism is unknown. One of the proteases involved in mitAß catabolism is the long insulin-degrading enzyme (IDE) isoform (IDE-Met(1)). However, the mechanisms of its expression are unknown, and its presence in brain is uncertain. We detected IDE-Met(1) in brain and showed that its expression is regulated by the mitochondrial biogenesis pathway (PGC-1α/NRF-1). A strong positive correlation between PGC-1α or NRF-1 and long IDE isoform transcripts was found in non-demented brains. This correlation was weaker in Alzheimer disease. In vitro inhibition of IDE increased mitAß and impaired mitochondrial respiration. These changes were restored by inhibition of γ-secretase or promotion of mitochondrial biogenesis. Our results suggest that IDE-Met(1) links the mitochondrial biogenesis pathway with mitAß levels and organelle functionality.
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Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Insulisina/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Doença de Alzheimer/genética , Secretases da Proteína Precursora do Amiloide/genética , Secretases da Proteína Precursora do Amiloide/metabolismo , Peptídeos beta-Amiloides/genética , Animais , Encéfalo/patologia , Células HEK293 , Células HeLa , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Humanos , Insulisina/genética , Mitocôndrias/genética , Mitocôndrias/patologia , Proteínas Mitocondriais/genética , Proteínas do Tecido Nervoso/genética , Fator 1 Nuclear Respiratório/genética , Fator 1 Nuclear Respiratório/metabolismo , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Ratos , Ratos Sprague-Dawley , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Neuronal connectivity and synaptic remodeling are fundamental substrates for higher brain functions. Understanding their dynamics in the mammalian allocortex emerges as a critical step to tackle the cellular basis of cognitive decline that occurs during normal aging and in neurodegenerative disorders. In this work we have designed a novel approach to assess alterations in the dynamics of functional and structural connectivity elicited by chronic cell-autonomous overexpression of the human amyloid precursor protein (hAPP). We have taken advantage of the fact that the hippocampus continuously generates new dentate granule cells (GCs) to probe morphofunctional development of GCs expressing different variants of hAPP in a healthy background. hAPP was expressed together with a fluorescent reporter in neural progenitor cells of the dentate gyrus of juvenile mice by retroviral delivery. Neuronal progeny was analyzed several days post infection (dpi). Amyloidogenic cleavage products of hAPP such as the ß-C terminal fragment (ß-CTF) induced a substantial reduction in glutamatergic connectivity at 21 dpi, at which time new GCs undergo active growth and synaptogenesis. Interestingly, this effect was transient, since the strength of glutamatergic inputs was normal by 35 dpi. This delay in glutamatergic synaptogenesis was paralleled by a decrease in dendritic length with no changes in spine density, consistent with a protracted dendritic development without alterations in synapse formation. Finally, similar defects in newborn GC development were observed by overexpression of α-CTF, a non-amyloidogenic cleavage product of hAPP. These results indicate that hAPP can elicit protracted dendritic development independently of the amyloidogenic processing pathway.
Assuntos
Precursor de Proteína beta-Amiloide/metabolismo , Dendritos/metabolismo , Hipocampo/citologia , Neurogênese , Precursor de Proteína beta-Amiloide/genética , Animais , Dendritos/fisiologia , Giro Denteado/citologia , Giro Denteado/crescimento & desenvolvimento , Giro Denteado/fisiologia , Potenciais Pós-Sinápticos Excitadores , Feminino , Hipocampo/crescimento & desenvolvimento , Hipocampo/fisiologia , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Rede Nervosa/citologia , Rede Nervosa/crescimento & desenvolvimento , Rede Nervosa/fisiologia , Células Receptoras Sensoriais/citologia , Células Receptoras Sensoriais/metabolismo , Células Receptoras Sensoriais/fisiologiaRESUMO
Cerebral amyloid ß (Aß) accumulation is pathogenically associated with sporadic Alzheimer's disease (SAD). BACE-1 is involved in Aß generation while insulin-degrading enzyme (IDE) partakes in Aß proteolytic clearance. Vulnerable regions in AD brains show increased BACE-1 protein levels and enzymatic activity while the opposite occurs with IDE. Another common feature in SAD brains is Notch1 overexpression. Here we demonstrate an increase in mRNA levels of Hey-1, a Notch target gene, and a decrease of IDE transcripts in the hippocampus of SAD brains as compared to controls. Transient transfection of Notch intracellular domain (NICD) in N2aSW cells, mouse neuroblastoma cells (N2a) stably expressing human amyloid precursor protein (APP) Swedish mutation, reduce IDE mRNA levels, promoting extracellular Aß accumulation. Also, NICD, HES-1 and Hey-1 overexpression result in decreased IDE proximal promoter activity. This effect was mediated by 2 functional sites located at -379/-372 and -310-303 from the first translation start site in the -575/-19 (556 bp) fragment of IDE proximal promoter. By site-directed mutagenesis of the IDE promoter region we reverted the inhibitory effect mediated by NICD transfection suggesting that these sites are indeed responsible for the Notch-mediated inhibition of the IDE gene expression. Intracranial injection of the Notch ligand JAG-1 in Tg2576 mice, expressing the Swedish mutation in human APP, induced overexpression of HES-1 and Hey-1 and reduction of IDE mRNA levels, respectively. Our results support our theory that a Notch-dependent IDE transcriptional modulation may impact on Aß metabolism providing a functional link between Notch signaling and the amyloidogenic pathway in SAD.
Assuntos
Precursor de Proteína beta-Amiloide/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas de Homeodomínio/metabolismo , Insulisina/metabolismo , Regiões Promotoras Genéticas , Transdução de Sinais/fisiologia , Transcrição Gênica , Secretases da Proteína Precursora do Amiloide/metabolismo , Precursor de Proteína beta-Amiloide/genética , Animais , Ácido Aspártico Endopeptidases/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Proteínas de Ciclo Celular/genética , Linhagem Celular , Hipocampo/metabolismo , Proteínas de Homeodomínio/genética , Humanos , Insulisina/genética , Camundongos , Ligação Proteica , Receptores Notch/genética , Receptores Notch/metabolismo , Fatores de Transcrição HES-1RESUMO
Interest in the role of melanin-concentrating hormone (MCH) in memory processes has increased in recent years, with some studies reporting memory-enhancing effects, while others report deleterious effects. Due to these discrepancies, this study seeks to provide new evidence about the role of MCH in memory consolidation and its relation with BDNF/TrkB system. To this end, in the first experiment, increased doses of MCH were acutely administered in both hippocampi to groups of male rats (25, 50, 200, and 500 ng). Microinjections were carried out immediately after finishing the sample trial of two hippocampal-dependent behavioral tasks: the Novel Object Recognition Test (NORT) and the modified Elevated Plus Maze (mEPM) test. Results indicated that a dose of 200 ng of MCH or higher impaired memory consolidation in both tasks. A second experiment was performed in which a dose of 200 ng of MCH was administered alone or co-administered with the MCHR-1 antagonist ATC-0175 at the end of the sample trial in the NORT. Results showed that MCH impaired memory consolidation, while the co-administration with ATC-0175 reverted this detrimental effect. Moreover, MCH induced a significant decrease in hippocampal MCHR-1 and TrkB expression with no modification in the expression of BDNF and NMDA receptor subunits NR1, NR2A, and NR2B. These results suggest that MCH in vivo elicits pro-amnesic effects in the rat hippocampus by decreasing the availability of its receptor and TrkB receptors, thus linking both endogenous systems to memory processes.
Assuntos
Fator Neurotrófico Derivado do Encéfalo , Consolidação da Memória , Hormônios Hipofisários , Receptor trkB , Receptores de Somatomedina , Animais , Masculino , Ratos , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Melaninas , Hormônios Hipofisários/metabolismo , Receptor trkB/metabolismo , Receptores de Somatomedina/metabolismoRESUMO
Amyloid-ß (Aß) peptides are intimately involved in the inflammatory pathology of atherosclerotic vascular disease (AVD) and Alzheimer's disease (AD). Although substantial amounts of these peptides are produced in the periphery, their role and significance to vascular disease outside the brain requires further investigation. Amyloid-ß peptides present in the walls of human aorta atherosclerotic lesions as well as activated and non-activated human platelets were isolated using sequential size-exclusion columns and HPLC reverse-phase methods. The Aß peptide isolates were quantified by ELISA and structurally analyzed using MALDI-TOF mass spectrometry procedures. Our experiments revealed that both aorta and platelets contained Aß peptides, predominately Aß40. The source of the Aß pool in aortic atherosclerosis lesions is probably the activated platelets and/or vascular wall cells expressing APP/PN2. Significant levels of Aß42 are present in the plasma, suggesting that this reservoir makes a minor contribution to atherosclerotic plaques. Our data reveal that although aortic atherosclerosis and AD cerebrovascular amyloidosis exhibit clearly divergent end-stage manifestations, both vascular diseases share some key pathophysiological promoting elements and pathways. Whether they happen to be deposited in vessels of the central nervous system or atherosclerotic plaques in the periphery, Aß peptides may promote and perhaps synergize chronic inflammatory processes which culminate in the degeneration, malfunction and ultimate destruction of arterial walls.
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Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Aterosclerose/metabolismo , Aterosclerose/patologia , Plaquetas/patologia , Mediadores da Inflamação/metabolismo , Placa Aterosclerótica/patologia , Idoso de 80 Anos ou mais , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/isolamento & purificação , Precursor de Proteína beta-Amiloide/metabolismo , Plaquetas/metabolismo , Cromatografia Líquida , Feminino , Humanos , Masculino , Placa Aterosclerótica/metabolismo , Ativação Plaquetária , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
The extension of processes of oligodendrocyte (OLG) and their precursor cells are crucial for migration, axonal contact and myelination. Here we show that a non-lethal oxidative stress induced by 3-nitropropionic acid (3-NP) elicited a rapid shortening of processes (~24%) in primary OLGs and in oligodendroglial cell line (OLN-93) cells (~36%) as compared with vehicle-exposed cells. This was reversible and prevented by antioxidants. Proteomics of OLG lysates with and without 3-NP treatment yielded collapsin response mediator protein 2 (CRMP-2) as a candidate effector molecule. Inhibition of rho kinase was sufficient to prevent process retraction in both OLGs and OLN-93 cells. Oxidative stress increased phosphorylation of CRMP-2 at T555 that was completely prevented by Y27632. Moreover, transfection of OLN-93 cells with the mutant CRMP-2 T555A which cannot be phosphorylated by rho kinase, prevented process shortening induced by 3-NP as compared with wild-type CRMP-2. Our results suggest a role for endogenous reactive oxygen species in a pathway that regulates OLG process extension. The vulnerability of late myelinated neurons in the adult brain and the presence of white matter pathology in human dementias warrant the study of this oligodendroglial pathway in the early stages of neurodegenerative conditions characterized by oxidative stress.
Assuntos
Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Oligodendroglia/metabolismo , Oligodendroglia/patologia , Estresse Oxidativo/fisiologia , Animais , Antioxidantes/farmacologia , Western Blotting , Imunofluorescência , Humanos , Imuno-Histoquímica , Mutagênese Sítio-Dirigida , Oligodendroglia/efeitos dos fármacos , Fosforilação , Reação em Cadeia da Polimerase , Ratos , Ratos Wistar , Espécies Reativas de Oxigênio/metabolismo , Espécies Reativas de Oxigênio/toxicidade , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , TransfecçãoRESUMO
Introduction: The metabolic routes altered in Alzheimer's disease (AD) brain are poorly understood. As the metabolic pathways are evolutionarily conserved, the metabolic profiles carried out in animal models of AD could be directly translated into human studies. Methods: We performed untargeted Nuclear Magnetic Resonance metabolomics in hippocampus of McGill-R-Thy1-APP transgenic (Tg) rats, a model of AD-like cerebral amyloidosis and the translational potential of these findings was assessed by targeted Gas Chromatography-Electron Impact-Mass Spectrometry in plasma of participants in the German longitudinal cohort AgeCoDe. Results: In rat hippocampus 26 metabolites were identified. Of these 26 metabolites, nine showed differences between rat genotypes that were nominally significant. Two of them presented partial least square-discriminant analysis (PLS-DA) loadings with the larger absolute weights and the highest Variable Importance in Projection (VIP) scores and were specifically assigned to nicotinamide adenine dinucleotide (NAD) and nicotinamide (Nam). NAD levels were significantly decreased in Tg rat brains as compared to controls. In agreement with these results, plasma of AD patients showed significantly reduced levels of Nam in respect to cognitively normal participants. In addition, high plasma levels of Nam showed a 27% risk reduction of progressing to AD dementia within the following 2.5 years, this hazard ratio is lost afterwards. Discussion: To our knowledge, this is the first report showing that a decrease of Nam plasma levels is observed couple of years before conversion to AD, thereby suggesting its potential use as biomarker for AD progression.
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We study the complex formation of a peptide betaAbetaAKLVFF, previously developed by our group, with Abeta(1-42) in aqueous solution. Circular dichroism spectroscopy is used to probe the interactions between betaAbetaAKLVFF and Abeta(1-42), and to study the secondary structure of the species in solution. Thioflavin T fluorescence spectroscopy shows that the population of fibers is higher in betaAbetaAKLVFF/Abeta(1-42) mixtures compared to pure Abeta(1-42) solutions. TEM and cryo-TEM demonstrate that co-incubation of betaAbetaAKLVFF with Abeta(1-42) causes the formation of extended dense networks of branched fibrils, very different from the straight fibrils observed for Abeta(1-42) alone. Neurotoxicity assays show that although betaAbetaAKLVFF alters the fibrillization of Abeta(1-42), it does not decrease the neurotoxicity, which suggests that toxic oligomeric Abeta(1-42) species are still present in the betaAbetaAKLVFF/Abeta(1-42) mixtures. Our results show that our designed peptide binds to Abeta(1-42) and changes the amyloid fibril morphology. This is shown to not necessarily translate into reduced toxicity.
Assuntos
Peptídeos beta-Amiloides/química , Amiloide/química , Oligopeptídeos/química , Fragmentos de Peptídeos/química , Sequência de Aminoácidos , Amiloide/efeitos dos fármacos , Animais , Benzotiazóis , Dicroísmo Circular , Microscopia Crioeletrônica , Microscopia Eletrônica de Transmissão , Neurônios/efeitos dos fármacos , Neurotoxinas/farmacologia , Oligopeptídeos/farmacologia , Oligopeptídeos/toxicidade , Estrutura Secundária de Proteína , Ratos , Espectrometria de Fluorescência , TiazóisRESUMO
Several studies suggest that the assembly of mitochondrial respiratory complexes into structures known as supercomplexes (SCs) may increase the efficiency of the electron transport chain, reducing the rate of production of reactive oxygen species. Therefore, the study of the (dis)assembly of SCs may be relevant for the understanding of mitochondrial dysfunction reported in brain aging and major neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). Here we briefly reviewed the biogenesis and structural properties of SCs, the impact of mtDNA mutations and mitochondrial dynamics on SCs assembly, the role of lipids on stabilization of SCs and the methodological limitations for the study of SCs. More specifically, we summarized what is known about mitochondrial dysfunction and SCs organization and activity in aging, AD and PD. We focused on the critical variables to take into account when postmortem tissues are used to study the (dis)assembly of SCs. Since few works have been performed to study SCs in AD and PD, the impact of SCs dysfunction on the alteration of brain energetics in these diseases remains poorly understood. The convergence of future progress in the study of SCs structure at high resolution and the refinement of animal models of AD and PD, as well as the use of iPSC-based and somatic cell-derived neurons, will be critical in understanding the biological relevance of the structural remodeling of SCs.
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Encéfalo/metabolismo , Metabolismo Energético/fisiologia , Mitocôndrias/metabolismo , Dinâmica Mitocondrial/fisiologia , Doenças Neurodegenerativas/metabolismo , Neurônios/metabolismo , Envelhecimento/metabolismo , Envelhecimento/patologia , Animais , Encéfalo/patologia , Complexo I de Transporte de Elétrons/genética , Complexo I de Transporte de Elétrons/metabolismo , Complexo IV da Cadeia de Transporte de Elétrons/genética , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Humanos , Mitocôndrias/patologia , Doenças Neurodegenerativas/patologia , Neurônios/patologia , Espécies Reativas de Oxigênio/metabolismoRESUMO
E7 is the major transforming activity in human papillomaviruses, a causal agent for cervical cancer. HPV16 E7 is a small protein with a natively unfolded domain for which dozens of specific cellular targets were described, and represents a prototypical oncoprotein among small DNA tumor viruses. The protein can form spherical oligomers with amyloid-like properties and chaperone activity. Conformation specific antibodies locate endogenous oligomeric E7 species in the cytosol of 3 model cell lines, strongly co-localizing with amyloid structures and dimeric E7 localizes to the nucleus. The cytosolic oligomeric E7 appear as the most abundant species in all cell systems tested. We show that nuclear E7 levels are replenished dynamically from the cytosolic pool and do not result from protein synthesis. Our results suggest that long-term events related to de-repression of E7 would cause accumulation of excess E7 into oligomeric species in the cytosol. These, together with the known target promiscuity of E7, may allow interactions with many of the non-pRb dependent targets described. This hypothesis is further supported by the detection of E7 oligomers in the cytosol of cancerous cells from tissue biopsies.
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Amiloide/química , Carcinoma Endometrioide/metabolismo , Transformação Celular Neoplásica , Citosol/metabolismo , Proteínas Oncogênicas Virais/metabolismo , Osteossarcoma/metabolismo , Neoplasias do Colo do Útero/metabolismo , Animais , Neoplasias Ósseas/metabolismo , Neoplasias Ósseas/patologia , Neoplasias Ósseas/virologia , Carcinoma Endometrioide/patologia , Carcinoma Endometrioide/virologia , Núcleo Celular/metabolismo , Feminino , Imunofluorescência , Humanos , Immunoblotting , Técnicas Imunoenzimáticas , Camundongos , Camundongos Endogâmicos BALB C , Proteínas Oncogênicas Virais/genética , Osteossarcoma/patologia , Osteossarcoma/virologia , Papillomaviridae , Proteínas E7 de Papillomavirus , Infecções por Papillomavirus/metabolismo , Infecções por Papillomavirus/patologia , Infecções por Papillomavirus/virologia , Transfecção , Células Tumorais Cultivadas , Neoplasias do Colo do Útero/patologia , Neoplasias do Colo do Útero/virologiaRESUMO
Alzheimer's disease (AD) is characterized by the accumulation of extracellular insoluble amyloid, primarily derived from polymerized amyloid-beta (Abeta) peptides. We characterized the chemical composition of the Abeta peptides deposited in the brain parenchyma and cerebrovascular walls of triple transgenic Tg-SwDI mice that produce a rapid and profuse Abeta accumulation. The processing of the N- and C-terminal regions of mutant AbetaPP differs substantially from humans because the brain parenchyma accumulates numerous, diffuse, nonfibrillar plaques, whereas the thalamic microvessels harbor overwhelming amounts of compact, fibrillar, thioflavine-S- and apolipoprotein E-positive amyloid deposits. The abundant accretion of vascular amyloid, despite low AbetaPP transgene expression levels, suggests that inefficient Abeta proteolysis because of conformational changes and dimerization may be key pathogenic factors in this animal model. The disruption of amyloid plaque cores by immunotherapy is accompanied by increased perivascular deposition in both humans and transgenic mice. This analogous susceptibility and response to the disruption of amyloid deposits suggests that Tg-SwDI mice provide an excellent model in which to study the functional aftermath of immunotherapeutic interventions. These mice might also reveal new avenues to promote amyloidogenic AbetaPP processing and fundamental insights into the faulty degradation and clearance of Abeta in AD, pivotal issues in understanding AD pathophysiology and the assessment of new therapeutic agents.
Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Angiopatia Amiloide Cerebral/metabolismo , Placa Amiloide/metabolismo , Doença de Alzheimer/patologia , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Apolipoproteínas E/metabolismo , Benzotiazóis , Angiopatia Amiloide Cerebral/patologia , Dimerização , Modelos Animais de Doenças , Humanos , Camundongos , Camundongos Transgênicos , Placa Amiloide/patologia , Conformação Proteica , Tiazóis/metabolismoRESUMO
BACKGROUND: We evaluated the amounts of amyloid beta (Abeta)) peptides in the central nervous system (CNS) and in reservoirs outside the CNS and their potential impact on Abeta plasma levels and Alzheimer's disease (AD) pathology. METHODS: Amyloid beta levels were measured in (1) the plasma of AD and nondemented (ND) controls in a longitudinal study, (2) the plasma of a cohort of AD patients receiving a cholinesterase inhibitor, and (3) the skeletal muscle, liver, aorta, platelets, leptomeningeal arteries, and in gray and white matter of AD and ND control subjects. RESULTS: Plasma Abeta levels fluctuated over time and among individuals, suggesting continuous contributions from brain and peripheral tissues and associations with reactive circulating proteins. Arteries with atherosclerosis had larger amounts of Abeta40 than disease-free vessels. Inactivated platelets contained more Abeta peptides than activated ones. Substantially more Abeta was present in liver samples from ND patients. Overall, AD brain and skeletal muscle contained increased levels of Abeta. CONCLUSIONS: Efforts to use plasma levels of Abeta peptides as AD biomarkers or disease-staging scales have failed. Peripheral tissues might contribute to both the circulating amyloid pool and AD pathology within the brain and its vasculature. The wide spread of plasma Abeta values is also due in part to the ability of Abeta to bind to a variety of plasma and membrane proteins. Sources outside the CNS must be accounted for because pharmacologic interventions to reduce cerebral amyloid are assessed by monitoring Abeta plasma levels. Furthermore, the long-range impact of Abeta immunotherapy on peripheral Abeta sources should also be considered.
Assuntos
Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/sangue , Biomarcadores/sangue , Encéfalo/metabolismo , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/tratamento farmacológico , Peptídeos beta-Amiloides/metabolismo , Aorta/metabolismo , Biomarcadores/metabolismo , Plaquetas/metabolismo , Inibidores da Colinesterase/uso terapêutico , Feminino , Humanos , Fígado/metabolismo , Estudos Longitudinais , Masculino , Artérias Meníngeas/metabolismo , Pessoa de Meia-Idade , Músculo Esquelético/metabolismoRESUMO
The global increase in life expectancy turns Alzheimer's disease (AD) into a growing problem. One of the distinctive features of AD is the excessive accumulation of amyloid-b (Ab) peptide in the brain. In recent years, a concept that has gained strength is that degradation of Ab by proteases in situ is an important mechanism that prevents cerebral peptide accumulation. Biochemical and genetic data have shown that insulin-degrading enzyme (IDE) participates in Ab and insulin homeostasis. IDE expression and activity are significantly decreased in AD brains compared to age-matched controls. Also, IDE is deposited with Ab in senile plaques and blood vessels, indicating a gross conformational change as a consequence of diverse post-translational mechanisms. These alterations in IDE distribution and activity may result in insufficient degradation of Ab and insulin, promoting the formation of Ab oligomers and hormone resistance. Both processes might play a fundamental part in neurodegeneration. The study of the clearance mechanisms of cerebral Ab will not only aid in the understanding AD pathogenesis but will also allow a better interpretation of ongoing clinical trials and the development of new therapeutic strategies.
Assuntos
Doença de Alzheimer/enzimologia , Peptídeos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Insulisina/metabolismo , Idoso de 80 Anos ou mais , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Humanos , HidróliseRESUMO
The accumulation and spreading of protein tau in the human brain are major features of neurodegenerative disorders known as tauopathies. In addition to several subcellular abnormalities, tau aggregation within neurons seems capable of triggering endoplasmic reticulum (ER) stress and the consequent unfolded protein response (UPR). In metazoans, full activation of a complex ER-UPR network may restore proteostasis and ER function or, if stress cannot be solved, commit cells to apoptosis. Due to these alternative outcomes (survival or death), the pharmacological manipulation of ER-UPR has become the focus of potential therapies in many human diseases, including tauopathies. Here we update and analyze the experimental data from human brain, cellular, and animal models linking tau accumulation and ER-UPR. We further discuss mechanistic aspects and put the ER-UPR into perspective as a possible therapeutic target in this group of diseases.